Disintegrating Compression Set Plug with Short Mandrel

ABSTRACT

A compression set sealing element preferably 85A-95A TDI-Ester Polyurethane is compressed axially and retained against extrusion by CEM anti-extrusion rings. The compressed state of the sealing element is locked in by a degradable lock ring assembly. The mandrel is secured to an upper end of a slip cone and a breakable slip ring is secured by a wireline setting tool until the set position is reached. The slip ring breaks into segments that are pulled up the slip cone as the setting tool pushes on a sleeve to axially compress the sealing element and lock in the set. The sealing element is retained against extrusion by CEM anti-extrusion rings. When the setting tool is removed a ball seat is exposed for delivery of a ball to build pressure into the formation for fracturing. The entirety of the plug then disintegrates from well fluid exposure.

RELATED APPLICATION

This application is a continuation in part of application Ser. No.14/677,415 filed on Apr. 2, 2015.

FIELD OF THE INVENTION

The field of the invention is plugs that disintegrate and moreparticularly plugs with compression set sealing elements thatdisintegrate and that further have a shortened mandrel to the top of aslip cone to facilitate the disintegration.

BACKGROUND OF THE INVENTION

Fracturing is a process to enhance hydrocarbon delivery from a formationto a surface location. The fracturing is frequently a sequential processwhere a plug is set and a perforating gun that was run in with the plugis released from the plug and shot into the formation to createfractures. These fractures are then extended with high pressure slurryof proppant or typically mostly sand to open the perforation and holdthem open by remaining in the perforation after the high pressure flowis cut off. The zone with the recently produced fractures from theperforating gun is sometimes isolated by dropping a ball on the seat ofthe plug to close off a passage through the plug so that pressure intothe formation can be built up to deliver the proppant and further openor propagate the initially made fractures with the perforating gun. Ingeneral the process repeats until the entire formation is fractured atwhich time the completion for production is undertaken. However, beforeproducing the plugs in aid of the fracturing need to be removed. Thetraditional way this was done was with a milling trip into the boreholeto mill up all the plugs. This took a long time and required the millingdebris to be removed from the borehole with circulation and/or withvarious debris retention devices.

Over time, various components of the plugs were made from materials thatwould disintegrate or otherwise fail over time after their purpose wasserved. This partial construction with disintegrating components stillrequired a milling trip before production could start but the benefitwas that the duration of the milling trip could be shortened as fewercomponents needed to be milled. For example U.S. 2011/0048743 hadanchors that disintegrated with a seal assembly that needed milling out.In U.S. 2014/0318761 a lock for a hydrostatically set packerdisintegrated to allow the packer to set. In U.S. Pat. No. 7,487,678o-ring piston seals needed to disintegrate to enable some functions of adownhole valve. In U.S. 2007/0051521 a frack ball dropped onto a frackplug would disintegrate in an application of a retrievable frack packer.Disintegrating slips are shown in use with a ramp expanded sealingelement are shown in U.S. 2013/0299185 and U.S. Pat. No. 8,959,504. Inthat same family a swage expanded seal that has a disintegrating agentin it is used as shown in FIGS. 9A and 9B of U.S. 2013/0300066. A sealthat has a degradable layer is shown in U.S. 2013/0025849. For highpressure application the common approach to sealing has been pushing aseal assembly up a ramp into contact with a surrounding tubular as shownin U.S. Pat. Nos. 8,109,340 and 7,748,467.

Slips made from disintegrating materials are described in U.S.2014/0262327. Grit applied to a slip with a smooth outer surface isdiscussed in U.S. 8,579,024. Slips that bite with an exterior surfaceroughness are described in WO2014170685A2.

What is needed and provided by the present invention is a packer or plugdesign that has degrading metallic components preferably made withcontrolled electrolytic materials (CEM) and sold under the brandIn-tallic by Baker Hughes Incorporated of Houston Tex. and described inU.S. 2011/0136707 and related applications filed the same day. Thesealing element is preferably 85A-95A TDI-Ester Polyurethane that isaxially compressed to increase in radial dimension. These materials canbe used in a compression set packer assembly such as a Model D packersold by Baker Hughes with modifications such as CEM anti extrusion ringsand locking system for the set. The mandrel is shortened to support thetop of the cone for the slips so that there is less bulk to the plug andit can disintegrate faster. The inventors have discovered that sealingin fracking applications can be achieved with a compression set packingelement that disintegrates. This goes contrary to the prevailingthinking that has focused on pushing sealing elements up ramps to get aseal or radially expanding rings from within with swage assemblies.Instead, the present invention combines the reliability of known plugdesigns that push slips out on a cone and then axially compress asealing element and lock the set in a combination with materials thatdegrade to reduce or eliminate subsequent drilling out. To aid thedisintegration process the mandrel is shortened to not go under the slipcone but instead to support the slip cone by its upper end so that thereis less mandrel bulk to disintegrate with no sacrifice in structuralintegrity. Moreover, incorporating a disintegrating feature into afamiliar and reliable basic plug layout gives confidence that the plugwill set and properly anchor and seal without undue componentcomplication or the need for high setting forces as would be needed inradial expansion with swages or axially forcing a seal assembly up aramp to a sealing position. A slip ring is provided with externalirregular surface that is coated with grip enhancing grit as part of aslip assembly that can disintegrate. The application technique takesinto account the sensitivity of disintegrating slip material to heatwhen the grit coating is adhered to the slip body. These and otheraspects of the present invention will be more readily apparent to thoseskilled in the art from a review of the description of the preferredembodiment and the associated drawing while recognizing that the fullscope of the invention is to be determined by the appended claims.

SUMMARY OF THE INVENTION

A compression set sealing element preferably 85A-95A TDI-EsterPolyurethane is compressed axially and retained against extrusion by CEManti-extrusion rings. The compressed state of the sealing element islocked in by a degradable lock ring assembly. The mandrel is secured toan upper end of a slip cone and a breakable slip ring is secured by awireline setting tool until the set position is reached. The slip ringbreaks into segments that are pulled up the slip cone as the settingtool pushes on a sleeve to axially compress the sealing element and lockin the set. The sealing element is retained against extrusion by CEManti-extrusion rings. When the setting tool is removed a ball seat isexposed for delivery of a ball to build pressure into the formation forfracturing. The entirety of the plug then disintegrates from well fluidexposure. A slip ring has external wickers and a coating of grit isapplied in a manner that preserves the strength of the disintegratingslip body for enhancement of grip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a section view of the disintegrating packer or plugin the run in position with the setting tool in support thereof;

FIG. 2 is a section view of a slip ring and cone in the run in position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the FIG. 1, a slip ring 10 is an initial ring structure ofslips that are circumferentially connected with breakable tabs that arenot shown so that on setting which forces ring 10 onto cone 12 theresulting slips 14 separate from each other and wedge themselves againstthe surrounding borehole wall that is not shown. A wireline setting tool16 of a type well known in the art and sold by Baker Hughes Incorporatedas a Model E-4 supports the plug 18 to the desired subterraneanlocation. The setting tool 16 pushes down on sleeve 20, which is a partof the setting tool 16 and comes out of the hole after the plug orpacker is set, in the direction of arrow 22. At the same time thesetting tool 16 pulls up on sub 24 until the shear stud 48 breaks whichallows release of the setting tool 16 from the plug or packer 18. Duringsetting the ring of individual slips 14 splits apart. Collet fingers 28initially push up bottom sub 26 which takes with it the slips 14 untilthey wedge against the borehole wall. The pushing down of sleeve 22compresses the sealing element assembly 32 axially and allows the bodylock ring assembly 34 to engage to prevent axial relaxation of sealingelement assembly 32 that is now axially compressed to the point that itsexternal radial dimension has increased to put surface 36 against thesurrounding wellbore wall that is not shown. The internal dimension ofthe sealing element assembly conforms to the cylindrical shape of theouter wall of the mandrel 50 and does not change as the sealing elementassembly 32 is axially collapsed. The axial compression of assembly 32also extends the anti-extrusion rings 38 and 40 against the boreholewall to retain the sealing element 42, which can be a single sleeve ormultiple sleeves, in between in the set position against the boreholewall. The seal rings 49 retain the sealing element 42 to the mandrel 50to prevent swabbing-off the sealing element 42 during the installationof the plug in the borehole. These plugs are typically installed inhorizontal wells and high rate fluid flow is used to push the plug tothe desired location. This fluid flow exerts a force to pull the sealingelement 42 off the Mandrel 50. Optionally an internal ring 44 can alsobe used under seal 42. Seal 42, ring 44, rings 38 and 40 or lockingmember 34 can also be made of polymers such as PC-PPDI, PC-MDI, PD-TDI,Ether-PPDI, Ether-MDI, Ether-TDI, Esther-PPDI, Ester-MDI, Ester-TDI orPGA. Ultimately pushing in the direction of arrow 22 and pulling in thedirection of arrow 46 breaks the shear stud 48, pushes slips 14 up cone12 and compresses seal 42 with the axial compression locked in with lockring assembly 34. The setting tool 16 comes out through the plug mandrel50. The plug mandrel 50 extends from the lock ring assembly 34 on theupper end to lower end 52 that has a thread 54 connected into upper end56 of the cone 12. Thread 54 is the amount of extension of the mandrel50 into the cone 12. Mandrel 50 and cone 12 have aligned passages formounting to the setting tool 16. Alternatively the mandrel 50 can beintegral with the cone 12.

Preferably the mandrel 50 including the lock ring assembly 34, the cone12, the slips 14, internal ring 44, seal rings 49 and the anti-extrusionrings 38 and 40 as well as the bottom sub 26 are all made of adisintegrating material that is preferably CEM or another material thatresponds to existing or added well fluids or exposure over time tothermal or chemical inputs. Similarly the sealing assembly 32 ispreferably made of 85A-95A TDI-Ester Polyurethane or a material thatdisintegrates under similar conditions as the balance of the plug orpacker. Notably the mandrel 50 that stays in the hole is made short byending it at the top of the cone 12 so that there is less of it todegrade so that the overall disintegration time is reduced.

In essence the slips 14 are not supported by the mandrel 50 but insteadwhen set are wedged between the borehole wall that is not shown and thecone 12.

Those skilled in the art will appreciate that what is presented is acompression set plug that can be used in fracturing or otherapplications such as stimulation or acidizing, for example, by simplydropping a ball that is not shown onto a seat 60 that becomes exposed onremoval of the setting tool 16. What was unexpected is the fact thatdegradable materials can be used in the context of a compression setsealing element with opposed degradable anti-extrusion rings and providea reliable seal along with the degradability feature. After years ofexperimentation with designs that form as seal in place that degrades aswell as designs that push seals up wedges or radially expand such sealswhile encountering a variety of issues that made such designsproblematic for cost or operational reliability reasons, the presentinvention is in a sense back to the future in that the basic elements ofa compression set packer have been fitted into an assembly that canreliably seal and disintegrate. Modifications have been further made tominimize the bulk of the packer or plug while retaining structuralintegrity to promote more rapid disintegration. The shorter mandrel alsopromotes the use of a larger bore through the plug or packer and exposesmore surface area to well fluids to accelerate the disintegrationprocess. Those skilled in the art will appreciate that the termsdisintegrate, degrade, fail, dissolve or other terms are meant to beused interchangeably to connote an end to functional utility of thestructure in the process of coming apart in pieces and ultimatelydisappearing or being circulated out to the surface.

Slip ring 10 is preferably made from magnesium but other materials suchas chrome steel alloys nickel alloys; stainless alloys; carbide alloys;copper alloys; bronze; brass; aluminum and zinc to name some examples.

Ring 10 has a surface roughness 60 that can have a grit coating 62 forenhanced grip. The application process utilizes two wires of desiredmaterials in a spray gun which facilitates a high current between them.The current causes the wires to melt while an air channel pushes theresulting grit onto the surface of the base metal. Parameters are setsuch that the particles create a rigid surface capable of producing ananti-slip feature, rather than a smooth, wear-resistant surface. Thiscoating may be additive to provide a thicker layer ranging from, but notlimited to, 0.010″-0.060″.

The benefit of this process for the magnesium material is that thisprocess does not create excessive surface temperature, which wouldtypically burn the magnesium.

The ring 10 has scores 46 that allow the ring to break into segments asthe swage 12 advances to then push the segments out further radially toengage the surrounding tubular.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below:

We claim:
 1. A plug or packer assembly for subterranean use, comprising:a mandrel having a cylindrical outer surface; a slip assembly and anactuator for said slip assembly; a seal assembly on said cylindricalouter surface of said mandrel, said cylindrical outer surface of saidmandrel representing a constant internal diameter of said seal assembly,said seal assembly actuated with axial compression of said seal assemblyto axially collapse said seal assembly while maintaining said constantinternal diameter and forcing said seal assembly by virtue of said axialcollapse into contact with a surrounding borehole wall; wherein saidmandrel, slip assembly, actuator for said slip assembly and said sealassembly comprise one or more materials that disintegrate over time atthe subterranean location.
 2. The assembly of claim 1, wherein: saidmandrel supports said actuator for said slip assembly adjacent an upperend of said actuator for said slip assembly.
 3. The assembly of claim 1,wherein: said mandrel terminates within said actuator for said slipassembly adjacent an upper end of said actuator for said slip assembly.4. The assembly of claim 1, wherein: said mandrel further comprises adisintegrating locking member to hold the axially compressed position ofsaid seal assembly.
 5. The assembly of claim 4, wherein: said sealassembly further comprises at least one anti-extrusion ring on at leastone end of said seal assembly, said anti-extrusion ring comprises adisintegrating material.
 6. The assembly of claim 5, wherein: said atleast one anti-extrusion ring comprises a plurality of anti-extrusionrings with at least one disposed on each of opposed ends of said sealassembly.
 7. The assembly of claim 1, wherein: said seal assemblycomprises a polymer.
 8. The assembly of claim 1, wherein: said mandrel,slip assembly and actuator for said slip assembly comprises a controlledelectrolytic material (CEM).
 9. The assembly of claim 4, wherein: saidlocking member comprises a controlled electrolytic material (CEM). 10.The assembly of claim 6, wherein: said anti-extrusion rings comprise acontrolled electrolytic material (CEM).
 11. The assembly of claim 1,wherein: said seal assembly comprising a seal having the shape of asleeve with an internal ring between said mandrel and an inside surfaceof said sleeve, said internal ring comprises a disintegrating material.12. The assembly of claim 11, wherein: said internal ring comprises apolymer.
 13. The assembly of claim 1, wherein: said actuator for saidslip assembly comprising a cone with a cone passage therethrough, saidmandrel having a mandrel passage therethrough that aligns with said conepassage.
 14. The assembly of claim 13, wherein: said mandrel is threadedto a top of said cone and said thread represents the extension of saidmandrel into said cone or said mandrel is made integral with said cone.15. The assembly of claim 6, wherein: said seal assembly comprises apolymer further comprising at least one from a group comprising:PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI, Ether-TDI, Esther-PPDI,Ester-MDI, Ester-TDI or PGA and TDI-Ester Polyurethane.
 16. The assemblyof claim 15, wherein: said mandrel, slip assembly and actuator for saidslip assembly comprises a controlled electrolytic material (CEM). 17.The assembly of claim 16, wherein: said locking member comprises acontrolled electrolytic material (CEM) or a polymer further comprisingat least one from a group comprising: PC-PPDI, PC-MDI, PD-TDI,Ether-PPDI, Ether-MDI, Ether-TDI, Esther-PPDI, Ester-MDI, Ester-TDI orPGA and TDI-Ester Polyurethane.
 18. The assembly of claim 17, wherein:said anti-extrusion rings comprise a controlled electrolytic material(CEM) or a polymer further comprising at least one from a groupcomprising: PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI, Ether-TDI,Esther-PPDI, Ester-MDI, Ester-TDI or PGA and TDI-Ester Polyurethane. 19.The assembly of claim 18, wherein: said seal assembly comprising a sealhaving the shape of a sleeve with an internal ring between said mandreland an inside surface of said sleeve, said internal ring comprisesdisintegrating material.
 20. The assembly of claim 19, wherein: saidinternal ring comprises a polymer further comprising at least one from agroup comprising: PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI,Ether-TDI, Esther-PPDI, Ester-MDI, Ester-TDI or PGA and TDI-EsterPolyurethane.
 21. The assembly of claim 1, wherein: said disintegrationover time occurs from exposure to naturally or artificially createdconditions at the subterranean location.
 22. The assembly of claim 1,wherein: said seal assembly comprises a polymer.
 23. The assembly ofclaim 7 wherein: said polymer comprises at least one from a groupcomprising: PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI, Ether-TDI,Esther-PPDI, Ester-MDI, Ester-TDI or PGA and TDI-Ester Polyurethane. 24.The assembly of claim 4, wherein: said polymer comprises at least onefrom a group comprising: PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI,Ether-TDI, Esther-PPDI, Ester-MDI, Ester-TDI or PGA and TDI-EsterPolyurethane.
 25. The assembly of claim 12, wherein: said polymercomprises at least one from a group comprising: PC-PPDI, PC-MDI, PD-TDI,Ether-PPDI, Ether-MDI, Ether-TDI, Esther-PPDI, Ester-MDI, Ester-TDI orPGA and TDI-Ester Polyurethane.
 26. The assembly of claim 6, wherein:said anti-extrusion rings comprise at least one from a group comprising:PC-PPDI, PC-MDI, PD-TDI, Ether-PPDI, Ether-MDI, Ether-TDI, Esther-PPDI,Ester-MDI, Ester-TDI or PGA and TDI-Ester Polyurethane.
 27. The assemblyof claim 11, wherein: said internal ring comprises a controlledelectrolytic material (CEM).
 28. The assembly of claim 1, wherein: saidseal assembly further comprises at least one disintegrating seal ringadjacent at least one end of a sealing element.
 29. The assembly ofclaim 28, wherein: said at least one seal ring comprises opposed sealrings adjacent opposed ends of said sealing element, said seal ringsfurther comprising a controlled electrolytic material (CEM).
 30. A welltreatment method, comprising: deploying the plug or packer of claim 1 toisolate a portion of a borehole; applying pressure against said plug orpacker.
 31. The method of claim 30, comprising: allowing said plug orpacker to disintegrate after said applying pressure.
 32. The assembly ofclaim 1, wherein: said slip assembly further comprises a roughened outersurface coated with at least one layer of grip enhancing grit.
 33. Theassembly of claim 32, wherein: said grit comprises melted wires creatingthe particles blown onto said outer surface.
 34. A method of applying agrit coating to a downhole component to enhance gripping capabilitycomprising: providing wires in a spray gun; disposing said wires in afluid channel; running current through said wires; creating the grit bycausing the wires to melt with said current in the fluid channel;delivering the resulting grit onto the surface of the base metal. 35.The method of claim 34, comprising: limiting heat applied to thecomponent with fluid driving the grit.
 36. The method of claim 34,comprising: applying the grit to a roughened outer surface of thecomponent which further comprises at least one slip.